Hi Mohammad,
Please find the below links that will help you to understand the functionality of the merger account in Detail. This requires a detailed study and implemnting the correct note according to the error.
http://wiki.scn.sap.com/wiki/display/CRM/Data+Cleansing?original_fqdn=wiki.sdn.sap.com
Everything About merger account by Kiruthika - http://scn.sap.com/docs/DOC-34851
Regards,
karthik J